These are examples of what can happen when students sneak food into Berkeley’s libraries — especially during dead week, the pre-finals study time officially known as RRR week (for reading, review, recitation). It starts Monday (April 30).

Rules prohibit bringing food and drink — anything but water in a bottle — into Berkeley’s libraries, says Barclay Ogden, director for library preservation. But he’s been around long enough — 31 years — to know it will happen, and part of his job is to try to head off the worst abuses with a few gentle reminders.

Among them is a display set up in a glass case right inside the front desk at Moffitt, a main undergraduate library. All night long during dead week, all seats at Moffitt are likely to be filled with cramming students, and, despite frequent pickups, by the end of the night trash cans might be overflowing with evidence of much-needed sustenance, sometimes even empty pizza boxes, as Ogden describes the scene.

Inside the display case, ants attack a chocolate-frosted donut, a puddle of coffee wrecks an ancient book, mice cavort amid sandwich wrappers, a soda can and moldy or insect-chewed documents — all simulations of realistic situations, using plastic vermin but real books.

The display shows that the damage caused by careless consumption goes beyond the yuck factor. Take coffee or soda spilled in books, for example.

“We don’t discover it until after it’s gotten moldy,” says Ogden. “At that point it’s a complete loss.”

Food, even crumbs and droplets, can attract bugs — ants and cockroaches are the main offenders, but beetles can move in too, some are big as two inches long, Ogden says. Mice, rats and even squirrels find their way in sometimes. Most invasions are discovered before they can become an infestation. Occasionally, pest control has to be called in to set traps.

“The same critters that will eat your pizza will go on and eat the books,” says Ogden. Furniture is a frequent casualty.

Hundreds of thousands of books needed to be moved to eradicate a major bug infestation a dozen years ago, Ogden recounts. “It was very expensive.”

Problems can crop up in any of the libraries, at any time, Ogden says. But Moffitt is a focus, especially during dead week, because that’s where problems tend to show up.

Students have had access to the main stacks for about 20 years now, and “overall it’s been a very good thing,” he says.

But the access comes with responsibilities, and “as a group undergraduates are not as far along in their education as grad students,” as he puts it. Most students are careful, but a few leave behind a mess. Hence the plastic vermin and squished ketchup packets.

“I’m not sure how common it is anymore, but it’s not unheard of for students to call for pizza and have it delivered to the library,” says Ogden — not a practice he condones.

“Food – they’re going to bring it in. What they do with it is important,” he says. “If they take their trash with them, that’s a help. People do need to eat and drink if they’re going to move into the library during dead week. Our goal is to do as little damage as possible.